The invention is based on a method for the angularly correct mounting of a fuel injection pump on an internal combustion engine, especially a Diesel engine. The injection pump, having been adjusted in terms of the supply quantity, onset supply and camshaft location is mounted on the engine in a working position with the crankshaft.
For the angularly correct mounting of a fuel injection pump, embodied either as a series pump or as a distributor-type pump, on the associated internal combustion engine, the following method is used in the predominant number of cases: The camshaft of the injection pump is rotated into a rotary position corresponding to the onset of supply and is held fixed in this rotary position. This position is ascertained previously by the so-called "overflow method" and is indicated by a slash mark placed on the pump housing or on some revolving part which is firmly connected with the drive shaft. In the overflow method, the static supply onset of the injection pump, which is already preset in terms of its pre-stroke, is searched for; that is, with the pressure valve removed the pump suction chamber is placed under the pressure of fuel and the camshaft is slowly turned until such time as the pump piston, during its upward stroke, closes the intake bore and the fuel ceases to flow out. In this rotary position, the mark indicating the onset of supply is then placed on the pump. Before the injection pump is mounted on the engine, both the camshaft of the injection pump and the crankshaft of the engine are brought into their respective positions for supply onset as indicated by markings and the injection pump is then subsequently secured on the engine.
This known method is too imprecise for the stricter exhaust gas regulations of the present time, and in addition it has the serious disadvantage that the slash mark cannot be seen from the outside, or can be seen only quite poorly, if the pump is mounted with an end flange to the gear box of the engine. In this case, and also when there are very close tolerances for the onset of supply, it is necessary to search anew for the onset of supply once the injection pump has been mounted on the engine and then to correct the mounting of the pump. A further disadvantage of the known method is the difference between the static supply onset which is measured in the known method and the actual dynamic supply onset as it occurs during engine operation.
A method has been made known in German Offenlegunsschrift No.27 00 878 and corresponding U.S. Pat. No. 4,167,926, which enables the mounting of a fuel injection pump on the associated internal combustion engine while taking into consideration the dynamic onset of fuel supply. In this method, a strobe light is triggered at a fixed test rpm by means of the supply onset signal measured by an electric supply onset signal transducer, and with the aid of the strobe light the angular position of the camshaft of the injection pump can be read out on a revolving scale relative to a fixed pointer. The read-out angular position is engraved on a plate on the injection pump. Before the injection pump is mounted on the engine, the camshaft of the injection pump is rotated into the ascertained rotary position and then mounted on the appropriately prepared engine. This method involves the danger of errors in reading, and when a test is made as to whether the mounting on the engine is correct, a supply onset signal transducer must be used. However, since the same test conditions cannot be provided for the engine as exist on a test bench in the factory where the injection pumps are made, this method has the disadvantage that in addition to the differing test conditions, the expense for measurement appliances is very high.